The invention relates to a differential pressure transducer consisting of a body of insulating material provided with film electrodes and of at least two electrically conductive diaphragms which form a capacitance in conjunction with each of the film electrodes, the capacitance being dependent on the diaphragm deflection. The film electrodes and diaphragms form closed, interconnected cavities which are filled with a liquid.
Such differential pressure transducers are used, for example, in flow measurement apparatus for determining the flow rate of a liquid through an aperture in a duct on the basis of the pressure drop measured on both sides of the aperture by means of a differential pressure transducer.
German Offenlegungsschrift 23 64 027 discloses a differential pressure transducer which consists of a metallic hollow cylinder with pressure measurement diaphragms welded to its faces. The hollow cylinder is filled with insulating material. The diaphragms enclose interconnected cavities which are filled with an incompressible liquid and form, in conjunction with fillm electrodes provided on the insulating material, capacitors whose capacitance depends on the pressure-induced diaphragm deflection. The diaphragms are made of metal and form part of an electrical circuit. The metallic diaphragms can carry an electrical potential, so that sparking between the diaphragms and grounded apparatus parts cannot be precluded. Therefore, the measurement of the flow rate of explosive liquids by means of the known differential pressure transducer involves the risk of explosions.